Conventional ultrasound (or “scanline based” ultrasound as used herein) utilizes a phased array controller to produce and steer a substantially linear transmit waveform. In order to produce a B-mode image, a sequence of such linear waveforms (or “scanlines”) may be produced and steered so as to scan across a region of interest. Echoes are received along each respective scanline. The individual scanlines from a complete scan may then be combined to form a complete image (sometimes referred to as a “sector scan” image).
A display method known as M-mode (or motion mode) imaging is commonly used in cardiology and other fields where it is desirable to view the motion of imaged objects. In some forms of M-mode imaging, echoes from a one-dimensional line are displayed over time relative to a static reference point in order to allow a clinician to evaluate movement of a particular structure (such as a cardiac wall or valve) over time. Because a traditional scanline-based ultrasound path is directional (along the scanline axis), available M-mode lines tend to be limited to paths along a scanline.
Generally, M-mode imaging provides a graphic indication of positions and movements of structures within a body over time. In some cases, a single stationary focused acoustic beam is fired at a high frame rate and the resulting M-mode images or lines are displayed side-by-side, providing an indication of the function of a heart over multiple heart cycles.